1. Field of the Invention
The invention relates to a method for determining a leak in a breast wall of a regenerative heat recuperator and is especially applicable to a ceramic heat recuperator such as a hot-blast stove for a blast furnace.
2. Description of the Prior Art
A ceramic heat recuperator generally has a combustion chamber and a checkerwork chamber, both of shaft shape, generally parallel to each other and separated by a breast wall. The combustion chamber is provided with inlet means for air and fuel and the checkerwork chamber is provided with an outlet port for the discharge of the burned combustion gases, herein called flue gases. The checkerwork chamber contains a checkerwork which is a stack of ceramic bricks having passages for the flue gases, as a heat storage medium.
In a first phase of operation, a fuel, usually gaseous, is burned with air in a burner built into the combustion chamber. The hot flue gases are led out of the combustion chamber into the checkerwork chamber in which the combustion gases give off sensible heat to the stacked bricks. In a second operating phase air is led in the opposite direction through the heat recuperator thereby taking with it heat from the checkerwork. The heated air leaves the heat recuperator via a hole in the combustion chamber and may be used for example as hot blast for a blast furnace.
The dividing wall between the combustion chamber and the checkerwork chamber is brought up to temperatures which vary greatly on the combustion chamber side and the checker chamber side, and particularly at the lower region in the recuperator where the burner is situated. In the breast wall itself and at locations bonding to the outer shell this may result in cracking. Cracks in the breast wall may extend from the inlet for combustion air and fuel up to the checkerwork. A quantity of combustion air escapes through the resulting crack towards the checkerwork chamber without participating in the combustion. One result is that the fuel is not totally burned and the flue gases contain carbon monoxide. In order to make the combustion total, the volume of combustion air to be supplied by pumps must be further increased. This makes the heat generator efficiency fall because of the increased pumping required. With large leaks the pump capacity may even be too low for supplying sufficient combustion air for a total combustion.
In the past various methods of testing have been used to determine a leak in a breast wall by measuring the concentration of a gas component in the flue gas. Gas components chosen for this were carbon monoxide and oxygen i.e. gases produced by the combustion or in the combustion air. An inconvenience of that method of testing is that no distinction can be made between the results of a badly functioning burner and a leak in the breast wall. Therefore, using sampling pipes projecting through the bottom of the heat generator, it has been attempted to extract gas from a position in the checkerwork chamber close to the breast wall and to compare the oxygen concentration occurring there with the oxygen concentration in the discharge gas. This method of testing requires arrangements which are difficult to install, and yet gives only little information about the extent of the leakage.